Detailed specific example of the strategies used by one country to prevent and control cholera

Cholera Prevention and Control Strategies in Bangladesh – A Geographic Case Study

1. Introduction

Bangladesh, a low‑lying deltaic nation, faces recurrent cholera outbreaks because its physical environment (rivers, floods, climate) intersects with rapid urbanisation and high population density. This case study shows how geographic analysis informs public‑health action and maps directly onto the Cambridge International AS & A Level Geography syllabus (Topics 4 & 5).

2. Geographic Context

2.1 Physical Setting & Location

• Bangladesh occupies the Ganges‑Brahmaputra‑Meghna (GBM) delta, covering 147 000 km².
• Major river basins: Ganges (Padma), Brahmaputra (Jamuna), Meghna and tributaries dominate surface‑water flow.
• Annual mean discharge ≈ 1 200 km³; monsoon rains (June–September) provide ≈ 80 % of total runoff.

2.2 Hydrology, River‑Channel Processes & Flood Hazard

• River‑channel dynamics: High sediment load (≈ 1 000 Mt yr⁻¹) drives rapid aggradation, lateral migration of thalweg, and formation of oxbow lakes. During the monsoon the hydrograph shows a sharp rise to peak discharge (≈ 35 000 m³ s⁻¹) within 2–3 days, followed by a prolonged recession phase that sustains flood‑plain inundation.
• Flood frequency: Seasonal flooding affects ≈ 30 % of the population each year, inundating latrines, wells and water‑storage tanks.
• Groundwater: Depth varies from 5 m (coastal) to >30 m (upland), creating reliance on shallow hand‑pumped wells vulnerable to surface contamination.
• Mass‑movement hazards: River‑bank collapse and debris flows are common during extreme monsoon peaks. The 2019 Jamuna‑bank failure displaced 12 000 people and temporarily contaminated downstream water sources, illustrating the link between geomorphological hazards and cholera risk.

2.3 Climate Variability & Change

• Monsoon intensity has risen 5 % since 1990, increasing peak discharge and flood extent.
• IPCC RCP 4.5 projections (2050) forecast a further 10–12 % rise in July‑September rainfall, extending the duration of high‑flow conditions.
• El Niño‑Southern‑Oscillation events can produce drought‑flood cycles, stressing water supplies and prompting temporary reliance on unsafe surface water.

2.4 Population, Migration & Structure

• Size & density: ≈ 170 million people; 1 200 people km⁻².
• Urban growth: Dhaka grew from 7 million (2000) to > 21 million (2023), overwhelming municipal water and sanitation systems.
• Internal migration: Rural‑to‑urban and peri‑urban movement creates “hot‑spot” settlements on flood‑prone lands.
• International migration: ≈ 13 million Bangladeshis work abroad (mainly Gulf states). Remittances fund household water‑treatment devices, yet return migration can re‑introduce pathogens to rural areas.
• Population structure: Age‑sex pyramid shows a broad base (≈ 35 % under 15 years). Children under five account for 60 % of cholera cases, highlighting the need for age‑targeted interventions.

2.5 Urban‑Area Management

• Dhaka Water‑Supply Master Plan (2020‑2035): Aims to increase piped coverage from 55 % to 85 % and to replace ageing pipe networks. Evaluation: Early phases have reduced intermittent supply, but implementation delays and informal settlements limit full impact.
• Slum‑upgrading programmes (e.g., “Urban Upgrading Project” in Mirpur): Provide pour‑flush latrines and community water points. Evaluation: Health surveys show a 22 % drop in diarrhoeal disease incidence, yet maintenance of facilities remains a challenge.

3. Cholera – Linking Environment, Water & Health

Cholera is transmitted by ingestion of Vibrio cholerae in contaminated water or food. In Bangladesh the disease pattern is strongly tied to seasonal flooding and water‑quality failures.

Indicator	Value
Annual cases (est.)	100 000 – 200 000
Case‑fatality rate (untreated)	0.5 % – 2 %
Highest‑incidence districts	Khulna, Barisal, Sylhet (river‑plain & flood‑prone)

Poor water infrastructure → Surface & groundwater contamination → Ingestion of V. cholerae → Outbreaks → Health‑system response (WASH, vaccination, surveillance)

4. Integrated Prevention & Control Strategies

All interventions are designed to interrupt the chain above and are matched to the geographic drivers identified in Section 2.

1. Water, Sanitation & Hygiene (WASH) Interventions
   • Installation of chlorination units at key nodes in municipal networks (Dhaka, Chittagong).
   • Construction of pour‑flush latrines and small‑scale sewerage in flood‑prone rural unions.
   • Household hand‑washing stations with soap; > 85 % of target villages now functional.
   • Geographic link: Targeted to flood‑plain districts where surface‑water contamination peaks during monsoon.
2. Mass Oral Cholera Vaccination (OCV) Campaigns
   • Two‑dose Shanchol schedule (65–80 % efficacy).
   • Priority groups: flood‑affected communities, schoolchildren, informal urban settlements.
   • Coverage: 70 % of high‑risk population (≈ 12 million) between 2018–2021.
   • Geographic link: Mobile teams deployed along river corridors and peri‑urban slums.
3. Surveillance & Early‑Warning System
   • 30 sentinel district hospitals equipped with rapid diagnostic kits.
   • Real‑time reporting via DHIS2 mobile app and SMS alerts to district health officers.
   • Integration with the National Climate Forecast Centre; alerts triggered when monsoon rainfall exceeds the 90th percentile.
   • Geographic link: GIS‑based risk maps overlay river‑discharge data with case reports.
4. Community Engagement & Health Education
   • Training of 4 500 community health workers on cholera prevention and water testing.
   • Multi‑media campaigns (radio, TV, social media) in Bengali and local dialects.
   • School curricula on safe water handling and sanitation.
   • DEI focus: Materials adapted for low‑literacy groups, women’s groups, and ethnic minorities (e.g., Chakma).
5. Infrastructure Development & Maintenance
   • Repair of > 2 000 km of damaged water pipes and replacement of 150 000 L storage tanks after the 2020 floods.
   • Routine water‑quality monitoring using portable test kits (E. coli, turbidity).
   • Investment in flood‑control (levees, drainage canals) in the GBM basin to reduce contamination pathways.
   • Geographic link: Prioritised for districts where > 70 % of households lack piped water.

5. Impact Assessment (2015‑2023)

Strategy	Implementation Period	Coverage (%)	Reduction in Incidence (%)
WASH interventions	2015‑2020	85	40
Mass OCV campaigns	2018‑2021	70	25
Surveillance & early warning	2016‑2022	90	15
Community engagement	2014‑2023	95	10
Infrastructure & flood control	2013‑2021	80	20

6. Geographic Data Supporting the Case Study

District (River Basin)	Avg. Annual Flood Days	Groundwater Depth (m)	Cholera Incidence (per 10 000)
Khulna (Ganges‑Padma)	45	8‑12	27
Barisal (Meghna)	38	10‑15	22
Sylhet (Surma)	30	12‑18	18
Dhaka (Urban)	12	5‑9	9

7. Systems‑Thinking Model of Cholera Transmission

Adapted SIR framework for a water‑borne disease:

$$ \frac{dS}{dt}= -\beta \, S \, I - u S,\qquad \frac{dI}{dt}= \beta \, S \, I - \gamma I,\qquad \frac{dR}{dt}= \gamma I + u S $$

• β (transmission rate) – reduced by chlorination, improved sanitation and flood‑control.
• γ (recovery rate) – increased by prompt treatment and lower pathogen loads.
• ν (vaccination rate) – proportion of susceptibles moved directly to the immune class via OCV.

Scenario modelling (2015‑2023) shows that a 30 % reduction in β combined with vaccinating 70 % of susceptibles (ν) reproduces the observed 30‑40 % decline in cholera incidence.

8. Syllabus Alignment Summary

• Paper 1 – Physical Geography
  • Hydrology: river‑basin dynamics, flood hydrograph, groundwater depth.
  • River processes: sediment load, thalweg migration, deposition on flood‑plains.
  • Atmospheric processes: monsoon intensity, RCP 4.5 climate projections.
  • Mass‑movement hazards: river‑bank collapse case study.
• Paper 2 – Human Geography
  • Population & migration: internal & international flows, age‑sex structure, push‑pull factors.
  • Water resources & management: supply‑demand balance, WASH interventions, flood‑control infrastructure.
  • Urban areas & management: Dhaka Water‑Supply Master Plan, slum‑upgrading evaluation.
• Key Concepts Covered: Scale, change over time, place, spatial variation, cause‑and‑effect, systems, environmental interactions, challenges & opportunities, diversity & inclusion.

9. Conclusion

Bangladesh’s cholera control programme demonstrates how a geographically‑informed, multi‑sectoral approach can reduce disease burden in a flood‑prone delta. By linking river‑channel processes, climate‑change projections, population dynamics and targeted infrastructure, the country has achieved measurable health gains. Ongoing monitoring, climate‑adapted water management and inclusive community participation are essential to sustain progress and to provide a replicable model for other vulnerable nations.